Interpolation device



Filed Oct. 21. 1965 pt 2, 1969 o. TROTSCHER 3,465,331

' INTERPOLATION DEVICE s Sheets-Sheet 1 Sept. 2, 1969 TROTSCHER3,465,331

' INTERPOLATION DEVICE Filed Oct. 21, 1965 5 Sheets-Sheet 2 Sept. 2,1969 o.1-Ro1'scHr-:R

INTERPOLATION DEVICE 5 Sheets-Sheet :5

Filed Oct. 21. 1965 United States Patent m 3,465,331 INTERPOLATIONDEVICE Otto Triitscher, Aalen, Wurttemberg, Germany, assignor to CarlZeiss-Stiftung, doing business as Carl Zeiss, Wurttemberg, Germany, acorporation of Germany Filed Oct. 21, 1965, Ser. No. 499,735

Claims priority, applicatilon Germany, Nov. 6, 1964,

Int. Cl. H041 3/00; H0 3k 13/00; G06f 7/38 US. Cl. 340-347 2 ClaimsABSTRACT OF THE DISCLOSURE An interpolation device for digitalinterpolation in which an electron beam is moved continuously in aclosed circular path over a plurality of electrically conductive screenelements arranged in a circle and extending radially from a commoncenter. The screen elements are arranged in at least three separategroups which are electrically separated from each other. The pulsesproduced by the screen elements are fed into a selection circuit whichpermits a prefix-correct counting of said pulses.

In the aforesaid patent specification are disclosed two basicallydifferent screen element arrangements which allow for counting withprefix consideration the interpolation values of a primary signal. Thetarget of the electron beam, for example, the anticathode of a cathoderay tube, consists in both of these prior arrangements of individuallyinsulated screen units having similar screen constants and being oifsetagainst each other by an amount equal to one quarter of the screenconstant. In one arrangement the two screen units are disposedconcentrically in. a single target plane, and in the other arrangement,the two screen units are located one in rear of the other along the axisof the cathode ray tube, whereby in the last mentioned case the screenstruck first by the electron beam is in the form of a grid or diaphragmscreen letting through only about 50% of the total electrons in thebeam.

, Both of these prior arrangements are difficult to employ in actualpractice. The first arrangement requires that the electron beamoscillate at a very high frequency in radial direction of the screenunits in order to scan over the inner as well as the outer unit. Toobtain such action of the electron beam entails complicated circuitry.The latter arrangement necessitates measures for rendering inefiiectivethe secondary electrons released at the diaphragm screen, because thecontrast of the original signal must be constant over the whole circularsurface of the screen unit in order to obtain reliably correct counting.

It is one object of the present invention to overcome these difficultiesby grouping the screen elements in cyclic Patented Sept. 2, 1969sequence into at least three separated screen element groups and byconnecting each group to an electrical selective circuit, whicharrangement makes possible a prefix-correct counting of pulses occurringat the screen elements.

In case the screen elements are arranged in a single target plane, thespaces or gaps between the single screen elements are preferably madeabout the same width as the width of the electron beam at the point ofimpingement. When observing this relationship, the hysteresis will be aminimum on direction reversal of counting.

According to another object of the invention, the screen elements ofadjacent groups are arranged so that the gaps left by one group aretaken by the elements of the other group lying in a plane slightly inrear of the first group. Thus it is possible by a given number of screenelements to arrange them Within a smaller diameter and in turn to employa smaller cathode ray tube.

The selective circuit connected to each screen element group includes,for instance, a bistable multivibrator or flip-flop in direct connectionto the output lead for preparing trigger tubes or thyratrons associatedwith each channel either for forward or backward counting, and includesfurthermore counting-pulse-generating monovibrators. The pulse releaseof the monovibrator is initiated by flipping of the appertainingbistable multivibrator in a predetermined direction. By a reversal ofthe counting pulses, the multivibrators are later returned to theiroriginal condition.

Fundamentally there is always a direction identification possible wheninformation groups follow in succession which consist of at least threeunrelated and independent informations. When designating the threeinformations, for example, with A, B and C, it is possible to arrangethe circuits in such a manner that by progressive counting from Athrough B to C, an addition will be performed;

whereas by a response of the information in reversed di- With sucharrangement, for instance, it is possible to obtain forward and backwardcounting of a hundreds inter-.

polation with four screen element groups of twenty-five elements each,when the element groups are insulated from one another and theirelements are intermeshed in regular order so that the elements of eachgroup are equally spaced around a common center.

In order to more fully'understand the invention, a detailed descriptionof a few preferred embodiments will now be given with reference-to theaccompanying draw-- ings, in which:

FIG. 1 is an elevation view of a screendisc carrying a four-grouparrangement of screen elements;

FIG. 2 illustrates diagrammatically a circuit diagram of a selectorcircuit suitablefor interpolating the. pulses derived from the screendisc of FIG. 1;

FIG. 3 is a diagram indicating the relationship between screen elementwidth, interspace width and width of the impinging electron beam; and

FIG. 4 shows a linearly stretched layout of screen elements disposed intwo adjacent parallel planes whereby the rear elements are located inthe spaces between the front elements.

The screen disc diagrammatically illustrated in FIG. 1 comprises severalelectrically conducting screen elements, the total number of which isdivisible by four, but only the screen elements numbered 1 to are shown.The screen elements are insulated from one another by being arranged inspaced relation from one another and by being inserted in anonconductive center core K. Furthermore, the screen elements areconnected as shown alternately in cyclic succession each to one of theindividually insulated ring conductors L1, L2, L3 and L4. In theembodiment shown, for example, the screen elements 1, 5, 9 and so forth(only the first three are shown) are connected to ring conductor L1, thescreen elements 2, 6, 10

r and so forth are connected'to ring conductor L2, the

screen elements 3, 7 and so forth, to ring conductor L3, and finallythe'screen elements 4, 8 and so forth, to ring conductor L4. Each one ofthe ring conductors L1, L2, L3 and L4 is connected to terminal contactsA, B, C and D, respectively, and these terminal contacts are groundedthrough resistors W1, W2, W3 and W4 respectively. An electron beamstriking substantially normal the face of the screen disc and travellingto trace a substantially circular path thereon, will strike successivelyevery screen element, and in striking will produce an electric charge inthat particular element. Such charges will flow through the respectivering conductor and resistor to ground, producing thereby a voltage atthe respective terminal contacts A, B, C or D.

The voltage so produced are utilized in a subsequent selector circuit ofwhich one example is schematically illustrated in FIG. 2. Here the fourvoltages or informations derived from the screen arrangement of FIG. 1are applied for forward and backward counting. For this purpose, thecircuit has four input channels A, B, C and D- with provisions forconnecting to the correspondingly marked terminal contacts of FIG. 1.The reference characters referring to components and elements belongingto a particular channel carry the corresponding subscript, i.e., A, B, Cor D. The first stage in each channel is an amplifier markedcorrespondingly S S S or 8;, followed by respective Schmitt triggers T TT or T The amplifiers are so designed that each time the electron beamtravels across a screen element, the output potential L at therespective trigger jumps to 0. It may be mentioned here that thetriggers may be omitted when the amplifiers are controlled to renderstep-rise output signals. The trigger output leads are connected each tothe left preparation input lead of the respective bistable flip-flop F FF or F Each flip-flop can accept at a time one of two stable potentialsteps L or O, and can be flipped into one or the other of theseconditions by corresponding input pulses. The diagonal lines marked onthe flip-flop circuit symbols are for indicating the condition of acertain flip-flop. It is'assumed that the fulllined diagonals indicatethe condition under which the left bottom output lead of the respectiveflip-flop has the potential 0 and the right bottom output lead thepotential L, while the diagonals in dash-lines indicate reversedpotentials. Connected to the left top input leads of all flip-flops is apulse generator G serving to introduce pulses of a considerably higherfrequency than the actual counting frequency. The left bottom outputleads of the flip-flops are connected each to the input of a forwardthyratron V V V V of one adjacent channel and also to the input of abackward thyratron R R R R of the other adjacent channel. These forwardand backward thyratrons are all in the form of plus-grids, i.e., theypass pulses only when both of their input connections receive a pulsesimultaneously. The right bottom output connections of the flip-flops FF F and F are connected to monovibrators M M M and M respectively, andthe latter again to the second input connections of both the forward andbackward thyratrons belonging to the same channel as the respectivemonovibrator. The monovibrators produce a counting pulse of definiteduration.

The output leads of all forward thyratrons V V V and V are all connectedto inputs of a thyratron V forming an Or-grid or barrier, i.e., itpasses each single pulse no matter on which one of the input leads itarrives; and the output leads of all backward thyratrons R R R and R areconnected to inputs of another thyratron R which is also in the form ofan Or-grid. The output leads of the thyratrons V and R are connectedrespectively to the forward counting device Z and the backward countingdevice Z and besides, both output leads to the inputs of a furtherthyratron T serving also as an Or-grid. The output lead of thyratron 'Tconnects through an interposed reversing stage U to all four right topinputs of the flip-flops F F The diodes 20-27, connected to the rightside input leads of the prepreparation circuits of the flip-flops servefor direction-depending coupling and uncoupling of adjacent flipflopcircuits.

The operation of the selector circuit illustrated in FIG. 2, whenconnected to a screen arrangement as shown in FIG. 1, is as follows:

Assuming that the electron beam at the beginning of its travel strikes,for example, first the screen element 3 (FIG. 1) connected to the outputterminal contact C which is joined to input of channel C (FIG. 2). Thepotential or voltage change resulting from the beam impact on screenelement 3 is thus passed through the amplifier S and, as amplified,causes trigger T to jump from potential L to potential 0. This actionreadies the associated flip-flop F so that pulses arriving from thepulse generator G are able to flip P into the counting conditionindicated by the diagonal shown in a dash line. The resulting voltagejump from L to O at the right bottom outlet of flip-flop F acts onmonovibrator M whose impulses, however, can pass neither thorughthyratron R nor V because these thyratrons are not yet readied. Byflipping of flip-flop F there are readied only the backward thyratron Rand the forward thyratron V which are both connected to the left bottomoutlet of this flip-flop now at potential L.

The counting position thus attained remains now temporarily in thechannel connected to lead C.

When now the electron beam continues on its path and travels from screenelement 3 to screen element 4 (FIG. 1), the channel connected toterminal D comes under the influence of a voltage surge caused by thestriking beam, and flip-flop F is acted on to change to the conditionindicated by the diagonal shown in a dash line. This change acts onmonovibrator M Whose impulse can pass only through the forward thyratronV since this thyratron has previously been readied by flipflop F Thecounting impulse thus passed can now progress through thyratron V to theforward counter Z of the counting device causing it to move one digit inthe positive counting direction. Moreover, this same impulse passesparallel to its first path also through the Orgrid T and, after reversalin the reversing stage U, as

negative impulse to the right top inlets of all four flipflops. However,only flip-flop P will be affected and returned to its originalcondition, because only this one is readied by the adjacent flip-flop Fby way of the diode 22. This flip action from potential 0 to L causes noimpulse at monovibrator M Consequently, only flip-flop F remains incounting position.

When now the electron beam, continuing in the same direction of travel,reaches screen element 5 (FIG. 1),

the channel connected to terminal A of the selector circuit becomesactive. The voltage surge, resulting from the impact of the electronbeam, causes in this channel similar occurrences of forward counting asdescribed in the previous paragraph with reference to channel D. Thiswill be clearly understood from FIG. 2.

The operations for backward counting will now be explained: Assuming forthis purpose that the electron beam reverses its direction of travel andmoves from screen element 4 to screen element 3 (FIG. 1). The result isa voltage surge again in channel 3. The subsequent counting impulse,leaving multivibrator M, can now pass only through thyratron R becauseonly this one is readied by the flip-flop F which has not been returnedbut remained in counting position as previously stated. The impulse,after passing through R progresses through backward thyratron R to thebackward counter Z of the counting device and reaches, along the sameparallel path as described with reference to the forward counting cycle,the right top inlets of the flip-flops, affecting now, however, onlyflip-flop F in returning it to its original condition. Namely, only thisflip-flop is now readied by the adjacent flip-flop P by way of the diode21.

Analogous occurrences take place in all other screen element circuitsand counting channels whenever the electron beam strikes a respectivescreen element. The circuits and functions of their components whenpassing a pulse through a particularchannel will be clear from FIGS. 1and 2, and the detailed description above.

' When arranging the screen elements in a single plane as, for example,shown in FIG. 1, care must be taken that the width of the spaces betweenthe individual screen elements is in proper relationship to the diameterof the electron beam at the point of impact. If, for instance, as shownin FIG. 3, the width D of the screen elements 1' and 2 is equal to thewidth D of the space between these elements and the diameter D of theelectron beam is considerably smaller, then there is produced during areversal of the counting direction (reversal of movement direction ofthe electron beam into opposite direction of travel) a hysteresis thatcan be equal to the width of the space D i.e., about 50% of the spacebetween the screen elements.

Since it is conventional to allow in known counting devices operatingwith photoelectric emitters only a hysteresis of about to it isessential that the width of the space D between the screen elements isnot considerably wider than the diameter D, of the electron beam in theplane of the face of the screen unit.

For example, if a screen unit of ten elements has an effective diameterof 20 mm. with a relationship of element width to interspace width ofone to one, and the diameter of the electron beam in the plane of thescreen unit is 0.5 mm., the hysteresis will be about 50%. When now, withthe same electron beam diameter, the interspace width is reduced to,say, 0.6 mm., the hysteresis will drop to about 10%.

Similar considerations apply to a cathode ray interpolator with codedscreen. Here it is also important that the relationship between gap andweb is coordinated with the diameter of the cathode ray so that atreversal of the rotational direction in the cathode ray motion, thehysteresis amounts to not more than about 10% to 20.%

In the aforedescribed embodiment of the invention, all of the screenelements are disposed in a single plane. With a great number of screenelements, such an arrangement leads to large diameter screen discs whichin turn require large cathode ray tubes because their face must includethe whole disc area. It is possible, however, to reduce this screen discdiameter for a given number of elements by distributing these elements,for example, in two adjacent parallel planes one in back of the other.An example of such an arrangement is shown in FIG. 4 and includes thescreen elements 1", 3", 5", 7" in the front plane toward the tubecathode and, in a parallel plane in spaced relation in rear thereof andin the interspaces between the front elements, the screen elements 2",4", 6", 8". The width of the spaces between the screen elements of thefront plane are equal to the width of the screen elements in this plane.FIG. 4 indicates the screen elements in a linear arrangement, but itwill be understood that the same principle can be employed in a circulararrangement of the screen element. The screen elements of sucharrangement, all insulated from one another, can be combined into fourscreen groups with output leads A, B, C and D, as illustrated in FIG. 1,and, in connection with a selector circuit of FIG. 2, can be used forprefix-correct counting.

With a screen disc having a total of ten screen elements, it isadvisable to divide this number into five groups of two elements each,for instance, the elements 1 and 6 for one pair, the elements 2 and 7for the second pair, 3 and 8 for the third pair, 4 and 9 for the fourthpair, 5 and 10 for the fifth pair. The five output leads of these fivepair groups can then be connected to a selector circuit like the oneillustrated in FIG. 2 but extended by another channel.

What I claim is:

1. An interpolation device for digital interpolation of period signalsequences employing a continuously revolving electron beam whichcontinuously moves in a closed circular path in rhythm of the signalfrequency, including a plurality of electrically conductive screenelements arranged to extend radially from a common center and spacedfrom each other for a successive subdivision of said closed circularpath, said screen elements being combined and arranged in cyclicsuccession alternately in at least three separate groups of screenswhich are electrically insulated from each other, means forming aselection circuit, and means for connecting said groups of screenelements to said selection circuit, said selection circuit includingmeans permitting a prefix-correct counting of the pulses produced bysaid screen elements, said selection circuit further including bistablemultivibrators, the inputs of which are connected each with the 'outputof said screen element groups and which prepare thyratrons associatedwith the individual channels for counting forward and in reverse, andimpulse producing monovibrators which create each a counting impulse ofdefinite duration as soon as the bistable multivibrator, which isarranged in front of said monovibrator, flips in a predetermineddirection from a stable position into the other, whereby the negativecounting impulses are returned to the multivibrators and the latter arereturned to their initial position.

2. An interpolation device for digital interpolation of period signalsequences employing a continuously revolving electron beam whichcontinuously moves in a closed circular path in rhythm of the signalfrequency, including a plurality of electrically conductive screenelements arranged to extend radially from a common center and spacedfrom each other for a successive subdivision of said closed circularpath, said screeen elements being combined and arranged in cyclicsuccession alternately in at least three separate groups of screenswhich are electrically insulated from each other, means forming aselection circuit, and means for connecting said groups of screenelements to said selection circuit, said selection circuit includingmeans permitting a prefix-correct counting of the pulses produced bysaid screen elements, said spaced screen elements being arranged inspaced parallel planes one behind the other and perpendicular to thelongitudinal axis of the electron beam, one plane having arrangedtherein along a circle a number of even numbered screen elements, andthe next adjacent plane having arranged therein along a circle a numberof oddnumbered screen elements, whereby the center portions of thescreen elements in one of said planes are disposed to cover the spacesbetween the screen elements arranged in the next adjacent plane.

References Cited UNITED STATES PATENTS i igg l at aliii 4; MAYNARD R.WILBUR, Primary Examiner Starr 340-347 M. K. WOLENSKY, AssistantExaminer Wingate 340347 X I Barwicz et a1 3158.5 10

Rantsch et a1. 340347X

